anyone using Itanium B-step support?

anyone using Itanium B-step support?

[James E Wilson]

The kernel still has an ITANIUM_BSTEP_SPECIFIC configure option, as of
2.6.8.1, which enables use of the gcc -mb-step option.  As far as I
know, this is the only user of the gcc/gas B-step support.  I am
skeptical that this support still works, and suggest that it be removed,
so that I can remove the gcc/gas B-step support.

The reason why this comes up now is because gas has support to emit
warnings in cases where extra nops must be emitted to avoid B-step
errata.  This is enabled by default.  At the time, this was useful to
ensure backwards compatibility, but now all it does is confuse end users
who have no idea what an Itanium B-step processor is.  To fix this, I
need to add an option to enable it, which means I need to fix gcc to
pass the option to gas, and I also need to fix the kernel to add the
option to aflags when CONFIG_ITANIUM_BSTEP_SPECIFIC.

However, rather than add more ITANIUM_BSTEP_SPECIFIC support to the
kernel, I think it makes more sense to obsolete it and remove it.
-- 
Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com

Re: anyone using Itanium B-step support?

[David Mosberger]

>>>>> On Thu, 27 Jan 2005 13:56:36 -0800, James E Wilson <wilson@specifixinc.com> said:

  Jim> However, rather than add more ITANIUM_BSTEP_SPECIFIC support to
  Jim> the kernel, I think it makes more sense to obsolete it and
  Jim> remove it.

I agree.  I happened to run into the warning just recently myself and
came to the same conclusion.

We probably still have some B-step Merceds in our lab but IIRC, it was
so rare to trigger the erratum that even on those boxes we can live
without the workaround just fine.  And it's not likely that anyone is
using such old prototype hardware for anything mission critical...

	--david

Re: anyone using Itanium B-step support?

[James E Wilson]

[-- Attachment #1: Type: text/plain, Size: 227 bytes --]

On Thu, 2005-01-27 at 13:56, James E Wilson wrote:
> However, rather than add more ITANIUM_BSTEP_SPECIFIC support to the
> kernel, I think it makes more sense to obsolete it and remove it.

Here is the change I am suggesting.


[-- Attachment #2: patch.bstep.remove --]
[-- Type: text/x-patch, Size: 896 bytes --]

*** Kconfig.orig	Sat Aug 14 03:56:22 2004
--- Kconfig	Thu Jan 27 17:16:51 2005
*************** config IA64_BRL_EMU
*** 134,147 ****
  	depends on ITANIUM
  	default y
  
- config ITANIUM_BSTEP_SPECIFIC
- 	bool "Itanium B-step specific code"
- 	depends on ITANIUM
- 	help
- 	  Select this option to build a kernel for an Itanium prototype system
- 	  with a B-step CPU.  You have a B-step CPU if the "revision" field in
- 	  /proc/cpuinfo has a value in the range from 1 to 4.
- 
  # align cache-sensitive data to 128 bytes
  config IA64_L1_CACHE_SHIFT
  	int
--- 134,139 ----
*** Makefile.orig	Sat Aug 14 03:54:48 2004
--- Makefile	Thu Jan 27 17:17:03 2005
*************** ifeq ($(GCC_VERSION),3)
*** 49,56 ****
   endif
  endif
  
- cflags-$(CONFIG_ITANIUM_BSTEP_SPECIFIC)	+= -mb-step
- 
  CFLAGS += $(cflags-y)
  head-y := arch/ia64/kernel/head.o arch/ia64/kernel/init_task.o
  
--- 49,54 ----

Re: anyone using Itanium B-step support?

[David Mosberger]

>>>>> On Thu, 27 Jan 2005 17:24:02 -0800, James E Wilson <wilson@tuliptree.org> said:

  James> On Thu, 2005-01-27 at 13:56, James E Wilson wrote:
  >> However, rather than add more ITANIUM_BSTEP_SPECIFIC support to
  >> the kernel, I think it makes more sense to obsolete it and remove
  >> it.

  James> Here is the change I am suggesting.

Looks fine to me.  I found one more reference to
CONFIG_ITANIUM_BSTEP_SPECIFIC in arch/ia64/configs/bigsur_defconfig.
Not that it really matters, but from a cleanliness perspective, we may
want to get rid of that at the same time.

I would have done it myself but there was no "Signed-off-by" trailer
in your patch so I think you may need to resend the patch anyhow
before Tony will take it (unless he judges the patch to be trivial
enough not to need this).

	--david

Re: anyone using Itanium B-step support?

[James E Wilson]

On Thu, 2005-01-27 at 17:54, David Mosberger wrote:
> Looks fine to me.  I found one more reference to
> CONFIG_ITANIUM_BSTEP_SPECIFIC in arch/ia64/configs/bigsur_defconfig.

I see no such file in my copy of linux-2.6.8.1 downloaded from
kernels.org, but yes, that should be fixed too.

> I would have done it myself but there was no "Signed-off-by" trailer
> in your patch so I think you may need to resend the patch anyhow

I know nothing about submitting linux kernel patches.  My patch is
completely untested, by the way, as I doubt that I can build a working
kernel without help.  It was more a suggestion than an actual patch.

Re: anyone using Itanium B-step support?

[David Mosberger]

>>>>> On Thu, 27 Jan 2005 18:32:49 -0800, James E Wilson <wilson@tuliptree.org> said:

  >> I would have done it myself but there was no "Signed-off-by"
  >> trailer in your patch so I think you may need to resend the patch
  >> anyhow

  James> I know nothing about submitting linux kernel patches.  My
  James> patch is completely untested, by the way, as I doubt that I
  James> can build a working kernel without help.  It was more a
  James> suggestion than an actual patch.

Ah, OK, in that case, here is a (compile-)tested patch.

Tony, please apply.

	--david

ia64: Remove Merced B-step support

Remove left-over support for Merced B-step CPUs as suggested by Jim
Wilson.

Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>

=== arch/ia64/Kconfig 1.85 vs edited ==--- 1.85/arch/ia64/Kconfig	2005-01-24 13:41:13 -08:00
+++ edited/arch/ia64/Kconfig	2005-01-27 22:05:34 -08:00
@@ -158,14 +158,6 @@
 	depends on ITANIUM
 	default y
 
-config ITANIUM_BSTEP_SPECIFIC
-	bool "Itanium B-step specific code"
-	depends on ITANIUM
-	help
-	  Select this option to build a kernel for an Itanium prototype system
-	  with a B-step CPU.  You have a B-step CPU if the "revision" field in
-	  /proc/cpuinfo has a value in the range from 1 to 4.
-
 # align cache-sensitive data to 128 bytes
 config IA64_L1_CACHE_SHIFT
 	int
=== arch/ia64/Makefile 1.74 vs edited ==--- 1.74/arch/ia64/Makefile	2005-01-14 15:52:52 -08:00
+++ edited/arch/ia64/Makefile	2005-01-27 22:05:43 -08:00
@@ -46,8 +46,6 @@
 	cflags-$(CONFIG_MCKINLEY)	+= -mtune=mckinley
 endif
 
-cflags-$(CONFIG_ITANIUM_BSTEP_SPECIFIC)	+= -mb-step
-
 CFLAGS += $(cflags-y)
 head-y := arch/ia64/kernel/head.o arch/ia64/kernel/init_task.o
 
=== arch/ia64/configs/bigsur_defconfig 1.2 vs edited ==--- 1.2/arch/ia64/configs/bigsur_defconfig	2004-11-30 08:48:16 -08:00
+++ edited/arch/ia64/configs/bigsur_defconfig	2005-01-27 22:05:20 -08:00
@@ -73,7 +73,6 @@
 CONFIG_IA64_PAGE_SIZE_16KB=y
 # CONFIG_IA64_PAGE_SIZE_64KB is not set
 CONFIG_IA64_BRL_EMU=y
-# CONFIG_ITANIUM_BSTEP_SPECIFIC is not set
 CONFIG_IA64_L1_CACHE_SHIFT=6
 # CONFIG_NUMA is not set
 # CONFIG_VIRTUAL_MEM_MAP is not set